The present invention relates to a sound board assembly for a musical instrument, which is suitable for use in, for example, a piano or the like.
As is well known, the piano is among the struck string musical instruments. A sound generating mechanism of the piano will be described with reference to FIG. 94 of the attached drawings. A hammer 1 is angularly moved in interlocking relation to the movement of a key or note to hit a string 2. The free oscillation or vibration of the string 2 excited by the hitting thereof drives a sound board assembly 3, which that is a sound radiator, through a string support section called a bridge 4. As a result, a sound is emitted from the sound board assembly 3. As will be understood from the above-described sound generating mechanism, the role of the sound board assembly 3 in the piano is extremely important. It is not too much to say that the characteristics of the sound of the piano are almost completely determined by the physical properties of the material of the sound board assembly 3.
There are two characteristics required of piano sound: a good response with respect to the hitting of the strings and a good elongation or spreading of the sound. Accordingly, it is necessary for the sound board assembly 3 to its characteristics which fulfill the above requirements. It has conventionally been considered that Picea woods such as spruce or the like are suitable as such material having the above-mentioned characteristic.
If the sound board assembly is made only from natural woods, the specific modulus of elasticity E/lo, where E is a Young's modulus and lo is density, is limited to values peculiar to the woods. Thus, there is a problem in that it is impossible to achieve sound generating efficiencies beyond a certain extent. In view of this, a sound board assembly has been developed as disclosed in, for example, Japanese Patent Unexamined Publication Nos. SHO 60-57894 and SHO 60-57895 in which the sound generating efficiency is raised to favorably generate sounds from low-pitched ranges to high-pitched ranges. In the sound board assembly, material consisting of cores in the sound board assembly of a laminate structure is selected, or sheets are interposed in the laminate structure, in order to increase the modulus of rigidity G and to reduce the internal friction loss Q.sup.-1 or the shear loss tangent tan delta.
Further, a sound board assembly has also been developed as disclosed in Japanese Patent Unexamined Publication No. SHO 57-136693, in which, in order to produce clear musical qualities (tone colors), carbon fibers arranged in the direction of the grain of the surface-layer plates of the sound board assembly are applied respectively to both sides of an internal-layer plate of the sound board assembly, to increase the modulus of longitudinal elasticity E and to reduce the shear loss tangent tan delta. With this sound board assembly, the damping factor is reduced due to internal friction.
That the above-described conventional sound board assembly exhibits the merit of the woody sound peculiar to a natural musical instrument, that is, a warmth of sound which is not metallic; however, this is insufficient. Thus, there is a problem in that the conventional sound board assembly is inferior in its audibility characteristics.